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United States Patent |
5,081,384
|
Rausch
|
January 14, 1992
|
Cooled electric motor protecting components from coolant
Abstract
A cooled electric motor comprising a releasable sealing cover element for
protecting electrical components, in particular, coil winding heads
located in end spaces between opposite end faces of a stator plate pack
and respective bearing shields. The cover can be removed for service in
cleaner environments.
Inventors:
|
Rausch; Hartmuth (Korschenbroich, DE)
|
Assignee:
|
Schorch GmbH (Munchen Gladbach, DE)
|
Appl. No.:
|
420350 |
Filed:
|
October 12, 1989 |
Current U.S. Class: |
310/63; 310/57 |
Intern'l Class: |
H02K 009/18; H02K 005/10 |
Field of Search: |
310/62,63,64,89,88,57,90
|
References Cited
U.S. Patent Documents
2592070 | Apr., 1952 | Robinson | 310/89.
|
2650316 | Aug., 1953 | Johns et al. | 310/63.
|
3445698 | May., 1969 | Miko | 310/89.
|
3610975 | Oct., 1971 | Onjanow | 310/63.
|
4406959 | Sep., 1983 | Harano et al. | 310/89.
|
4742257 | May., 1988 | Carpenter | 310/57.
|
4745314 | May., 1988 | Nakano | 310/57.
|
Primary Examiner: Stephan; Steven L.
Assistant Examiner: Rebsch; D. L.
Attorney, Agent or Firm: Striker; Michael J.
Claims
What is claimed as new and desired to be protected by Letters Patent is set
forth in the appended claims:
1. A cooled electric motor for higher protection systems than IP23,
comprising a stator including a stator plate pack having opposite end
faces; a rotor disposed in said stator; bearing shields arranged at
opposite sides of said electric motor, defining, with said opposite end
faces of said stator plate pack, end spaces, and having inlet and outlet
openings for conducting cooling medium; electrical components located in
said end spaces; and releasable cap-like sealing cover means hermetically
separating said electrical components from the cooling medium in said end
spaces.
2. A cooled electric motor as set forth in claim 1, wherein said electrical
components comprise coil winding heads projecting beyond said opposite end
faces of said stator plate pack, said electric motor further comprising
fan means for cooling said winding heads.
3. A cooled electric motor as set forth in claim 2, wherein said releasable
cap-like sealing cover means is formed with cooling fins.
4. A cooled electric motor as set forth in claim 2, wherein said stator
plate pack is radially enlarged and has a plurality of continuous axial
bores.
5. A cooled electric motor as set forth in claim 2, further comprising a
casing including two members defining end plates and fitted onto
peripheral locating surfaces at said opposite end faces and connected to
said stator plate pack.
6. A cooled electric motor as set forth in claim 4, further comprising
threaded bolts extending through at least several of said axial bores in
said stator plate pack for attaching said bearing shield to each other and
to said stator plate pack.
7. A cooled electric motor as set forth in claim 2, wherein said bearing
shields have an identical construction.
8. A cooled electric motor as set forth in claim 2, wherein said electric
motor further comprises a connection box and a rating plate, said bearing
shields having attachment surfaces for securing thereto said connection
box and said rating plate.
Description
BACKGROUND OF THE INVENTION
The invention relates to an air cooled electric motor having a stator, a
rotor, end plates and a fan, for higher protection systems than IP 23.
Standard electric motors for individual protection systems, for example, IP
23 or IP 54 (DIN 40050) are very different in construction. This means
that special components must be produced and stored for each motor
construction. The reason for the different constructions is the various
regulations which must be observed concerning the movement of the cooling
air, in dependence on the protection system. The electric motor is used in
the higher protection systems where components of a machine must be so
protected against foreign bodies or the ingress of water that it results
in not enough cooling air being supplied to the winding heads of the coils
in the stator. Frequently the construction having cooling fins on the
external periphery is selected for these higher protection systems. A fan
attached to an end face of the motor supplies cooling air in the axial
direction through the channels which are formed between the fins and are
open at the top, although the cooling result at the start and end of the
motor differs greatly. Due to the cooling channels open at the top, the
cooling air passes over and cools the casing jacket only over a portion of
its length, while the cooling air increasingly escapes upwards out of the
channels in the axial direction of the casing, so that the end of the
motor casing is inadequately cooled. With the lower protection systems,
the fan attached to an end face of the motor sucks or forces surrounding
air through openings in the end plate disposed at the axial end of the
motor remote from the fan and forces such air in the axial direction
through the free spaces in the motor. Examples of the different
construction of conventional standard motors are shown in FIGS. 1 and 2.
FIG. 1 illustrates an electric motor of low protection system, for
example, IP 23, while FIG. 2 shows a standard motor of higher protection
system, for example, IP 54. As can be readily seen, in the two kinds of
standard motor the casings are very differently constructed.
SUMMARY OF THE INVENTION
It is an object of the invention to provide casings of identical
construction and means which make possible intensive cooling for higher
protection systems, in the interests of standardizing electric motors for
low and also higher protective systems.
The object of the invention is achieved by providing electric motors which
are characterized by having a releasable cover to protect the coil winding
heads in the end spaces of the motor between the end face of the stator
plate pack and the end plate, the cover hermetically separating the spaces
containing the electrical elements from the spaces cooled by the flowing
cooling medium.
Preferably the cover takes the form of a dish, a ring, or an annular disc
and can have cooling fins.
The stator plate pack can also be radially enlarged and be formed with a
number of continuous axial bores.
Furthermore the motor can be built without a casing in such a way that two
pot-like bearing shields are directly secured each of them to oppossed
ends as is, i.e. known from DE-AS 538 900.
The Swiss Patent 406,396 discloses that the pot-like bearing shields can be
clamped to the stator plate pack by threaded bolts inserted through
certain of the axial bores in the stator plate pack. However, the parts
can also be welded to the stator plate pack.
The radial enlargement of the stator plate pack, which was known per se,
for example, from DE-AS 873 718, allows the accommodation of axial cooling
channels which create satisfactory cooling conditions over the whole
length of the motor.
By abolishing the casing, the possibility of identical forming of the two
bearing shields for both sides of the machine results in reducing the
diversity of parts.
According to the invention, for higher protection systems than IP 23, an
additional releasable cover is provided in the form of a dish, a ring or
an annular disc to protect the electrical elements, more particularly the
winding heads of the coils in the stator, such cover being inserted in the
end spaces of the motor between the end faces of the stator plate pack and
the bearing shields and being sealed at the contact surfaces, in
accordance with the particular requirements, against the entry of
aggressive or wet atmosphere, foreign (dust) particles or water. The cover
parts can then be identical for machines of different protection systems.
With a divided casing comprising the two bearing shields provided on both
sides and also at the top with attachment surfaces for the connection box
and the rating plate, the connection box and the rating plate can be
disposed on any of the three sides dependent on accessibility.
The different length of the stator plate pack in electric motors of
different protection system can be compensated either by an additional
casing spacer ring, or a number of holes or slots for the attaching screws
in the base of the casing.
Independently of its protection system, the construction of an electric
motor according to the invention offers the following advantages:
the same electrically inactive parts can be used for motors of different
protection systems. This standardization represents a considerable saving
in manufacturing and warehousing costs;
the cooling of all motors is appreciably intensified, however they may be
constructed so that not only the fan output, but also air noises can be
reduced;
the heat transfer from the plate pack to the cooling air takes place
directly and not, as hitherto, via the casing;
the noises caused by magnetic excitations are reduced by strengthening the
yoke in the stator plate pack and cannot be radially propagated to freely
oscillating parts of the casing (casing jacket, webs, cooling fins and
others);
the absence of the jacket casing in the central portion of the motor saves
weight, if the radial enlargement of the stator plate pack is compensated
by an axial shortening of the pack due to the more intensive cooling.
The invention will be explained in greater detail with reference to
specific embodiments of the electric motor according to the invention,
with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a partially cross-sectional side elevaton view of; an electric
motor constructed as an air-cooled rotary electric motor such as is
selected, for example, for protection system IP 23,
FIG. 2 shows a partially cross-sectional side elevation view of a
conventional standard motor, for example, of protection system IP 44,
FIG. 3 shows a partially cross-sectional side elevation view of an electric
motor constructed as an air-cooled rotary electric motor such as is
selected for example, for protection system IP 23, with additional
cap-like cover of the winding heads for protection systems higher than IP
23,
FIG. 4 shows a partially cross-sectoinal side elevation view of a
conventional standard motor, for example, of protection system IP 44, the
radial casing openings are closed for protecting the winding heads by ring
covers.
FIG. 5 shows a partially cross-sectional side elevation view of an electric
motor according to the invention for low and higher protection systems,
with suction ventilation and a dish-type cover of the winding heads, and
FIG. 6 shows a partially cross-sectional side elevation view of another
embodiment of an electric motor according to the invention for low and
higher protection system, with pressure ventilation and an annular cover
for the winding heads.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the drawings like elements have like references.
Referring to FIG. 1, an air-cooled rotary electric motor, for example, of
protection system IP 23, comprises a stator plate pack 1, coils 2 in the
stator with the winding heads 3 projecting on both sides beyond the ends
of the stator plate pack 1, and a rotor 4 which is disposed concentrically
in the stator and has at its axial ends fan blades 5 for intensifying the
cooling of the winding heads 3.
The stator and rotor are enclosed by a casing 6. Flanged on to the opposite
axial ends of the casing 6 are bearing shields 7 formed with openings 8, 9
for entry and exit of cooling air into and out of the inside of the casing
6. The cooling air is sucked through the inside of the casing 6 by a
suction fan 29 attached to the shaft 10 of the rotor 4 at one end of the
casing 6. The path followed by the cooling air through the inside of the
casing 6 is shown by arrows 13. Deflector plates 14 ensure that air flows
around the winding heads 3.
Formed on the motor casing are feet 11 having holes, through which screws
extend attaching the motor to the foundation, and an eyelet 12 for the
insertion of a crane hook.
For a higher protection system than IP 23, the electrical components of the
motor, more particularly the coil winding heads 3, are screened by a
releasable cover. In the embodiment shown in FIG. 3, the releasable cover
takes the form of a cap 20. The cap 20 extends between the bearing shied 7
and stator plate pack 1 in the two end spaces of the motor. The air
circulation inside the space closed off from atmosphere via caps 20 is
indicated by arrows 15. The cooling air moved by a suction fan 29 is
sucked from atmosphere through the openings 8 into the motor and flows in
the axial direction around the cap 20 through the annular duct formed
between the stator plate pack 1 and the casing 6, in the direction
indicated by arrows 13.
With caps 20 covering the electrical components, the same motor can also be
operated for higher protection systems than IP 23. In the embodiment
illustrated in FIG. 4 the same motor can be used for higher protection
systems than IP 23, merely by the insertion of a ring 21 which
hermetically seals the radial openings 25 in the casing 6.
The bearing shields 7 are constructed as pot-like castings for greater
standardization of components, the bearing shields on the drive side and
on the fan side are of identical construction.
In the embodiment illustrated in FIG. 5 the two winding heads 3, which
project beyond the end faces of the stator plate pack 1, are again each
covered by a cap 20 for electric motors of higher protection system than
IP 23. Each cap 20 extends between the bearing shield 7 and the opposite
end face of the stator plate pack 1, seals being inserted at both contact
surfaces 22, 23.
Instead of the suction fan 29 (FIG. 5) a pressure fan 30 as shown in FIG. 6
can be used, in which the flow of cooling air 13 moves in the opposite
direction. As shown in FIG. 6, the higher protection system than IP 23 is
achieved according to the invention by the feature that the coil winding
heads and electrical components between the bearing shield 7 and the
stator plate pack 1 are covered by rings 21 which are again sealed against
the outside cooling air by seals inserted at the contact surfaces 22, 23.
The bearing shields 7 shown in FIG. 6 are formed with openings 8 for the
entry and exit of the cooling air only in the outer edge zone.
On the bearing shields 7 attachment surfaces 24 are provided on three sides
offset in relation to one another by 90.degree., two at the side and one
at the top, for the attachment of a connection box or a rating plate.
While the invention has been illustrated and described as embodied in an
electric motor, it is not intended to be limited to the details shown,
since various modifications and structural changes may be made without
departing in any way from the spirit of the present invention.
Without further analysis, the foregoing will so fully reveal the gist of
the present invention that others can, by applying current knowledge,
readily adapt it for various applications without omitting features that,
from the standpoint of prior art, fairly constitute essential
characteristics of the generic or specific aspects of this invention.
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